Method and device for controlling an internal combustion engine in accordance with operating parameters

ABSTRACT

A method and a device for controlling an internal combustion engine as a function of performance characteristics such as load, engine speed, a corrected value for the intake air temperature being used for the control, the corrected value being obtained from the following formula:whereTANSK=corrected value of the intake air temperature,T1=value (TANS) of the intake air temperature remote from the internal combustion engine determined by calculation or measured,TWS=value of the mean temperature of the intake manifold,f=weighting factor ranging from 0 to 1.

FIELD OF INVENTION

The present invention is based on a method as well as a device forcontrolling an internal combustion engine as a function of performancecharacteristics, such as air filling, engine speed, engine temperatureand intake air temperature. As far as the intake air temperature inparticular is concerned, it has a number of effects on the behavior ofthe internal combustion engine. With otherwise identical ambientconditions, a higher intake air temperature produces effects including ahigher knock tendency, improved evaporation of the fuels, reduced wallfilm formation of the fuels on the interior walls of the intake manifoldas well as a reduction of the volume of air taken in and accordingly ofthe quantity of fuel required. Against this background, modern controlsfor internal combustion engines condition the intake air temperature,for which an appropriate sensor is inevitably required.

BACKGROUND INFORMATION

German Patent No. 44 35 419 A1, which relates to a “control system forproportioning the fuel of an internal combustion engine” and in whichthe intake air temperature value is used among other things for thedetermination of a warm start case, may be pointed out as exemplary ofthe extensive conventional methods in connection with the use of asignal of the intake air temperature in the context of the control of aninternal combustion engine.

Primarily reasons relating to space requirements in the area of theinternal combustion engine are the reason that sensors for the intakeair temperature are usually not mounted in the immediate vicinity of theinternal combustion engine but rather, for example, in the air filterhousing, in a mass air flow meter, in the throttle valve connector or incombination with an intake manifold pressure sensor. The temperaturemeasured with these sensors does not then correspond to the actualintake temperature in the vicinity of the intake valve which is relevantto the operation of the internal combustion engine when the intake aircan become heated on the warm walls of the intake manifold on its pathto the internal combustion engine. In internal combustion engines withexhaust gas recirculation, there is the additional heating of the intakeair by an admixture of the hot exhaust gas.

It has now been shown that it is not always possible to obtain optimalresults in relation to the influence of the intake air temperature withthe conventional systems.

SUMMARY OF THE INVENTION

An object of the present invention is to specify a method as well as adevice to make possible a determination of the intake air temperaturewhich is relevant to the control of the internal combustion engine.

The present invention makes it possible to model the intake airtemperature of an internal combustion engine in the vicinity of theintake valves by approximation. The basis for this is measurement of theintake air temperature upstream in the intake path, the heating of theintake air in the intake manifold on its way to the intake valves beingadditionally taken into account. In the case of exhaust gasrecirculation, its contribution to the heating of the intake air isadditionally included.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an internal combustion engine with an intake manifold andan exhaust pipe.

FIG. 2 shows a block diagram of a signal processing for a formation of acorrected value of an intake air temperature.

FIG. 3 shows a block diagram of the signal processing for the formationof a value of a mean temperature of the intake manifold.

FIG. 4 shows a block diagram of the signal processing for the formationof the corrected value of the intake air temperature with an exhaust gasrecirculation.

FIG. 5 shows a block diagram of the signal processing for the formationof a value of the temperature of a recirculated exhaust gas.

DETAILED DESCRIPTION

FIG. 1 shows an overview of an internal combustion engine together withthe intake manifold and exhaust pipe. The internal combustion engineitself is identified as 10 and one of the cylinders or combustionchambers as 11. The bottom of the combustion chamber is limited by apiston 12 and the top is limited by at least an intake valve 13 and anexhaust valve 14. In this connection, intake valve 13 forms thedownstream end of an intake manifold 15 in which a throttle valve 16 isarranged further upstream. An exhaust pipe 17 is drawn in on the outputside of the internal combustion engine. A connecting line 18 betweenexhaust pipe 17 and intake manifold 15 makes exhaust gas recirculationpossible, whose volume is adjustable via a controllable valve which isnot shown here.

To describe and explain the present invention temperature values areadditionally entered in FIG. 1. Thus the intake air temperature beforethrottle valve 16 has a value identified as TANS; after the throttlevalve, it has a value T1. The mean temperature of the intake manifold isidentified as TWS. In the immediate area of input valve 13, the intaketemperature has the value TANSK, which corresponds to a corrected intakeair temperature value. After the exhaust valve, the exhaust gases havean exhaust gas temperature TAbgas. Finally, an additional value for therecirculated exhaust gas is drawn in in the area of the opening ofexhaust gas recirculation line 18 into intake manifold 15 as TAGR.

An object of the present invention is to specify a value for thecorrected intake air temperature TANSK on the basis of availablemeasured and control values. This purpose is served by signal processingas indicated in a block diagram in FIG. 2. Values for intake airtemperature TANS (block 20), mean intake manifold temperature TWS (block21) and the air volume (block 22) are supplied at the input side in thisrepresentation of FIG. 2. The signal of the corrected intake airtemperature TANSK is available at an output 23.

The corrected value of the intake air temperature TANSK is formedaccording to the formula

TANSK=T 1+(TWS−T 1)*f

in which

TANSK=corrected value of the intake air temperature,

T1=value (TANS) of the intake air temperature remote from the internalcombustion engine determined by calculation or measured,

TWS=value of the mean temperature of the intake manifold and

f=weighting factor ranging from 0 to 1.

To supply the corrected value of intake air temperature TANSK, accordingto FIG. 2, signal T1 or TANS arrives at a summing point 24, whose secondinput receives the output signal supplied by a multiplication point 25.For its part, this multiplication point 25 receives a differential valuebetween the value of the mean temperature of intake manifold TWS and thevalue TANS or T1. At the second input of multiplication point 25, outputsignal f of a characteristic 26 is supplied, whose input variable is airvolume (22).

Supplementary to this or as an alternative, the output signal of acharacteristic map 27 can be supplied to multiplication point 25, theinput variables of the characteristic map being signals for engine speedand load (28, 29).

A comparison of the representation of FIG. 2 with the formula indicatedabove makes it clear that weighting factor f is formed on the basis ofsignals for air volume 22 and/or engine speed 28 as well as load 29.

It is essential for this weighting factor f to be a function ofperformance characteristics, these performance characteristics beingcharacteristic of the air flow to the internal combustion engine. Inthis sense, a signal in relation to the throttle valve angle as well asthe pressure in the intake manifold, for example, could be used as well.

The block diagram of the signal processing of FIG. 2 requires theknowledge of the mean temperature value of intake manifold TWS. FIG. 3shows a possibility for the formation of a corresponding temperaturevalue based on various input variables. In this connection, the elementsknown from FIG. 2 are provided with the reference numbers already usedthere. A sensor for the temperature of the internal combustion engineTMOT is identified as 30. A signal T1 is supplied via block 31. In thisconnection, T1 corresponds to intake air temperature TANS in cases inwhich no exhaust gas circulation occurs. With a view to a generalrepresentation, however, this signal value T1 was shown separately inFIG. 3. A signal relating to vehicle speed is supplied via a sensor 32.

The output signals from blocks 20 and 31 are each supplied to amultiplication point 34 and 35, respectively. On the output side, thesetwo multiplication points 34 and 35 are connected to an addition point36, to which signal TMOT is also supplied. The composite signal formedrepresents the enumerator in an adjoining division point 37, whoseoutput via a low pass 38 in turn ultimately corresponds to output signalTWS as the mean temperature of the intake manifold.

Vehicle speed signal 32 arrives at a characteristic 40, whose output isconnected to both multiplication point 34, as well as an addition point41, which in turn supplies the denominator signal for division point 37.Correspondingly, a characteristic 43 follows block 22 for therepresentation of an air volume signal, the output of the characteristicforming the second signal of multiplication point 35 and also beingsupplied to addition point 41. A constant value from a constant valuememory 44 is additionally supplied to this addition point. Finally, anadditional characteristic 45 is provided which receives air volumesignal 22 as its input signal and determines the time constant of thefilter or low pass 38 on the output side.

The combined circuitry shown in FIG. 3 can be expressed by the followingformula:

TWS(unfiltered)=(TMOT+TANS*K 1)/(1+K 2)

where

TMOT=internal combustion engine temperature, water temperature

TANS=measured value of the intake air temperature remote from theinternal combustion engine

K1=characteristic value as a function of vehicle speed and/or air volume

K2=characteristic value as a function of vehicle speed and air volume(FIG. 3).

FIG. 4 corresponds largely with the representation of FIG. 2 with thedifference that the influences in connection with exhaust gasrecirculation are additionally included. According to thisrepresentation, T1 is obtained as the air intake temperature value T1remote from the internal combustion engine which is determined bycalculation as

T 1=TANS+AGR rate*(TAGR−TANS)

in which

AGR rate=the rate of the recirculated exhaust gas and

TAGR=the temperature of the recirculated exhaust gas.

To form the signal value for T1, a value for the temperature of therecirculated exhaust gas TAGR (block 50) and a rate for the recirculatedexhaust gas (AGR rate 51) are processed as input variables. In asubtraction point 52, the difference between the temperature values ofthe recirculated exhaust gas and the intake air temperature is formedand subsequently multiplied with the exhaust gas recirculation rate in amultiplication point 53. The sum of the output signals of multiplicationpoint 53 and of the intake air temperature then forms temperature valueT1 for the intake air-exhaust gas mixture downstream of throttle valve16 in the area of the opening point of exhaust gas recirculation pipe 18into intake manifold 15.

The temperature signal required for the recirculated exhaust gas inconnection with the signal processing of FIG. 4 can be formed fromvarious measured or calculated variables corresponding to the blockdiagram of FIG. 5. Thus the temperature value of the recirculatedexhaust gas according to FIG. 5 is obtained as a low pass filteredsignal as a function of the values for intake air temperature, enginespeed, load and the volume of the recirculated exhaust gas (AGR volume).A control signal for the actuator in the exhaust gas recirculation linewhich processes as a function of performance characteristics may serve,for example, as a measure of this.

According to FIG. 5, an estimated value for the exhaust gas temperatureTAbgas downstream of exhaust valves 14 is formed based on the signalsfor engine speed and load (28, 29) via a characteristic map 55. Thedifference between the value TAbgas and intake air temperature TANS isdetermined in a difference forming point 56; it is subsequentlymultiplied with a weighting factor in multiplication point 57 andarrives at an addition point 58 together with a value for intake airtemperature TANS. On the output side, addition point 58 is connected tothe input of a downstream filter 59 which may be formed, for example, asa low pass and ultimately supplies a signal value for the temperature ofthe recirculated exhaust gas (TAbgas). To take into account of thevolume of the recirculated exhaust gas on the temperature of therecirculated exhaust gas, the value of the AGR volume is guided via onecharacteristic 61 and 62 each to multiplication point 57 and to filter59, respectively, to influence the filter constant of filter 59.

The signal representation of the individual figures makes it clear thatthe basic idea of the present invention is to specify a method and adevice for the approximate determination of the temperature of theintake air in the vicinity of the intake valves, the thermal timeconstant of the intake manifold being taken into account as well as theinfluence of an external exhaust gas recirculation.

What is claimed is:
 1. A method for controlling an internal combustionengine, comprising the steps of: determining, using one of a calculationprocedure and a measurement procedure, a value of an intake airtemperature remote from the internal combustion engine; determining acorrected value of the intake air temperature according to the followingformula: TANSK=T 1+(TWS−T 1)*f, wherein TANSK is the corrected value, T1is the value of the intake air temperature, TWS is a mean temperaturevalue of an intake manifold, and f is a weighting factor ranging between0 and 1; and controlling the internal combustion engine as a function ofperformance characteristics which include the corrected value.
 2. Themethod according to claim 1, wherein the performance characteristicsinclude a load, an engine speed, a temperature of the internalcombustion engine and the intake air temperature.
 3. The methodaccording to claim 1, further comprising the step of: determining theweighting factor as a function of the performance characteristics. 4.The method according to claim 3, further comprising the step of:determining the weighting factor as a function of an air flow volume inthe intake manifold.
 5. The method according to claim 3, furthercomprising the step of: determining the weighting factor as a functionof an engine speed and a load.
 6. The method according to claim 1,further comprising the step of: determining the mean temperature valueof the intake manifold as a function of a weighted mean of a temperatureof the internal combustion engine and a measured value of the intake airtemperature.
 7. The method according to claim 6, further comprising thestep of: determining the weighted mean as a function of the performancecharacteristics.
 8. The method according to claim 6, wherein theperformance characteristics include one of a load and an intake airvolume.
 9. A device for controlling an internal combustion engine,comprising: a controller determining a corrected value of an intake airtemperature using the following formula: TANSK=T 1+(TWS−T 1)*f whereinTANSK is the corrected value, T1 is a value of the intake airtemperature remote from the internal combustion engine which isdetermined using one of a calculation procedure and a measurementprocedure, TWS is a value of a mean temperature of an intake manifold,and f is a weighting factor ranging between 0 and 1, wherein thecontroller controls internal combustion engine as a function of thecorrected value.
 10. A method for controlling an internal combustionengine, comprising the steps of: determining, using one of a calculationprocedure and a measurement procedure, a value of an intake airtemperature remote from the internal combustion engine; determining acorrected value of the intake air temperature according to the followingformula: TANSK=T 1+(TWS−T 1)*f, wherein TANSK is the corrected value, T1is the value of the intake air temperature, TWS is a mean temperaturevalue of an intake manifold, and f is a weighting factor ranging between0 and 1; controlling the internal combustion engine as a function ofperformance characteristics which include the corrected value;determining the mean temperature value of the intake manifold as afunction of a weighted mean of a temperature of the internal combustionengine and the measured value of the intake air temperature; anddetermining the weighted mean as a function of the performancecharacteristics, wherein the performance characteristics include avehicle speed.
 11. A method for controlling an internal combustionengine, comprising the steps of: determining, using one of a calculationprocedure and a measurement procedure, a value of an intake airtemperature remote from the internal combustion engine; determining acorrected value of the intake air temperature according to the followingformula: TANSK=T 1+(TWS−T 1)*f, wherein TANSK is the corrected value, T1is the value of the intake air temperature, TWS is a mean temperaturevalue of an intake manifold, and f is a weighting factor ranging between0 and 1; controlling the internal combustion engine as a function ofperformance characteristics which include the corrected value;determining the mean temperature value of the intake manifold as afunction of a weighted mean of a temperature of the internal combustionengine and the measured value of the intake air temperature; determininga first characteristic value as a function of at least one of a vehiclespeed and an air volume; determining a second characteristic value as afunction of the vehicle speed and the air volume; and determining themean temperature value of the intake manifold according to the formula:TWS=(TMOT+TANS*K 1)/(1+K 2), wherein TMOT is the temperature of theinternal combustion engine, TANS is the measured value of the intake airtemperature, K1 is the first characteristic value, and K2 is the secondcharacteristic value.
 12. A method for controlling an internalcombustion engine, comprising the steps of: determining, using one of acalculation procedure and a measurement procedure, a value of an intakeair temperature remote from the internal combustion engine; determininga corrected value of the intake air temperature according to thefollowing formula: TANSK=T 1+(TWS−T 1)*f, wherein TANSK is the correctedvalue, T1 is the value of the intake air temperature, TWS is a meantemperature value of an intake manifold, and f is a weighting factorranging between 0 and 1; controlling the internal combustion engine as afunction of performance characteristics which include the correctedvalue; and determining the mean temperature value of the intake manifoldusing a filter time constant and a performance characteristic-dependenttime constant.
 13. A method for controlling an internal combustionengine, comprising the steps of: determining, using one of a calculationprocedure and a measurement procedure, a value of an intake airtemperature remote from the internal combustion engine; determining acorrected value of the intake air temperature according to the followingformula: TANSK=T 1+(TWS−T 1)*f, wherein TANSK is the corrected value, T1is the value of the intake air temperature, TWS is a mean temperaturevalue of an intake manifold, and f is a weighting factor ranging between0 and 1; controlling the internal combustion engine as a function ofperformance characteristics which include the corrected value; anddetermining the value of the intake air temperature according to thefollowing formula: T 1=TANS+AGR rate*(TAGR−TANS), wherein AGR rate is arate of a recirculated exhaust gas and TAGR is a temperature of therecirculated exhaust gas.
 14. The method according to claim 13, furthercomprising the steps of: estimating the temperature of the recirculatedexhaust gas as a function of a low pass-filtered weighted mean of theexhaust gas temperature and the measured value of the intake airtemperature; and determining the weighting factor and a filter timeconstant as a function of a gas flow rate in an exhaust gasrecirculation line.